Boulter J, Patrick J
J Biol Chem. 1979 Jul 10;254(13):5652-7.
Incubation of a nonfusing muscle cell line, BC3H1, with concanavalin A (Con A) results in a maximum decrease of 35% in the cell's ability to bind alpha-bungarotoxin (alpha-BuTx). The Con A-induced inhibition of 125I-alpha-BuTx binding is reversible and the degree of inhibition parallels the degree of saturation of Con A binding sites on the cell surface. The maximum level of Con A-induced inhibition of 125I-alpha-BuTx binding is not affected by increasing the time of incubation in Con A, using higher concentrations of Con A or by increasing the time of incubation in the presence of 125I-alpha-BuTx. In addition, all BC3H1 cells in culture are sensitive to the Con A-induced inhibition of 125I-alpha-BuTx binding. A comparison of the pseudo-first order rate constants for 125I-alpha-BuTx binding to untreated (8.6 x 10(4) M-1 S-1) and Con A-treated (5.4 x 10(4) M-1 S-1) BC3H1 cells, however, shows that those acetylcholine receptors in Con A-treated cells which bind 125I-alpha-BuTx do so with a lowered apparent affinity. Partial inhibition of toxin-binding capacity is not a consequence of two classes of acetylcholine receptors on the cell surface. Furthermore, individual receptors experience partial inhibition of their binding capacity by Con A, resulting in receptors with at least one binding site blocked and at least one site available for alpha-BuTx binding.
用伴刀豆球蛋白A（Con A）孵育非融合性肌肉细胞系BC3H1，会导致细胞结合α-银环蛇毒素（α-BuTx）的能力最大降低35%。Con A诱导的对125I-α-BuTx结合的抑制是可逆的，并且抑制程度与细胞表面Con A结合位点的饱和程度平行。Con A诱导的对125I-α-BuTx结合的最大抑制水平不受延长Con A孵育时间、使用更高浓度的Con A或延长125I-α-BuTx存在下的孵育时间的影响。此外，培养中的所有BC3H1细胞对Con A诱导的125I-α-BuTx结合抑制均敏感。然而，比较125I-α-BuTx与未处理的（8.6×10⁴ M⁻¹ S⁻¹）和Con A处理的（5.4×10⁴ M⁻¹ S⁻¹）BC3H1细胞结合的伪一级速率常数表明，Con A处理的细胞中那些结合125I-α-BuTx的乙酰胆碱受体的表观亲和力降低。毒素结合能力的部分抑制不是细胞表面两类乙酰胆碱受体的结果。此外，单个受体的结合能力会受到Con A的部分抑制，导致受体至少有一个结合位点被阻断，至少有一个位点可用于α-BuTx结合。
